Modern computer data storage systems, such as storage area networks (SAN) in enterprise environments often use the Fibre Channel (FC) network technology to provide high-speed (e.g., 2 to 16 gigabit/second) data transfers. A Fibre Channel network comprises a number of ports that are connected together, where a port is any entity that actively communicates over the network (either optical fiber or copper), where a port is usually implemented in a device such as disk storage or a Fibre Channel switch. The Fibre Channel protocol transports SCSI commands over Fibre Channel networks, and network topologies include point-to-point, arbitrated loop (devices in a ring), and switched fabric (devices/loops connected through switches). The Fibre Channel protocol comprises five layers in which a protocol mapping layer (FC4) encapsulates application protocols (i.e., SCSI or IP) into protocol data units (PDUs) for delivery to the physical layers (FC2 to FC0).
The SCSI (Small Computer System Interface) standards used by Fibre Channel networks define certain commands, protocols and electrical/optical interface characteristics for connected devices, such as hard disks, tape drives, and controllers. In data storage networks, a SCSI initiator is typically a computer that initiates a SCSI session by sending a SCSI command, and SCSI target is a data storage device that responds to initiators' commands and provides the required input/output data transfers.
In typical storage network systems, a logical unit number (LUN) is used to identify a logical unit, which is a device addressed by the SCSI protocol or SAN protocols that encapsulate SCSI, such as Fibre Channel or iSCSI networks. A LUN may be used with any device that supports read/write I/O (input/output) operations, and often refers to a logical disk as created on a SAN. In present systems, the configuration of LUN mapping on large numbers of SCSI target endpoints is serialized. That is, reassigning LUNs to different endpoints is done serially, one endpoint at a time. This is disruptive to ongoing I/O operations and takes longer to complete, especially for systems with many endpoints/LUNs. For example, in a current implementation of data domain operating system (DDOS), the system supports relatively few SCSI target endpoints (e.g., up to 8) and fewer LUNs (e.g., up to 640). As storage network operating systems (e.g., DDOS) scale up to support large numbers of SCSI target endpoints and large numbers of LUNS, the configuration of the endpoints with the LUN mapping compounds with the overhead of the current configuration approach.
A current approach configures the LUNs on the endpoints based on unique identifiers (IDs) assigned to each endpoint that is limited to 2 bytes. This limits the number of SCSI target endpoints that can be supported to 16. As stated above, another limitation comes with the serialized approach to configuring a LUN on multiple SCSI target endpoints, so that each time a LUN mapping is configured on an endpoint a suspend I/O activity operation must be performed to stop accepting new I/O commands and drain the outstanding I/O command to completion before the configuration can be completed. This can be disruptive with features that allow endpoints to migrate during failover and failback and other high availability (HA) network features.
What is needed is a LUN mapping scheme for large numbers of SCSI target endpoints that simultaneously configures the LUN mapping on multiple SCSI target endpoints with minimal disruption to customer backups and that also reduces the time required for endpoint migration and failover/failback operations.
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